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Bluetongue

Animal Health investigates all incidents of suspected notifiable disease. If you suspect signs of Bluetongue disease, you must immediately notify your local Animal Health office.

THE RISK TO YOUR ANIMALS

Bluetongue is a disease that can affect all ruminants, including sheep, cattle, deer, goats and camelids (camels, llamas, alpacas, guanaco and vicuña). Although sheep are usually most severely affected, cattle may sometimes display milder clinical signs and may potentially act as an undetected reservoir of disease, helping to keep infection circulating.

The disease, caused by a virus spread by vectors (biting midges), affects ruminants but not pigs, horses, dogs or humans. When a midge bites an infected animal, the virus passes to the midge in the blood meal and the virus then multiples within the midge. The length of time between the midge taking a blood meal from an infected animal and then becoming capable of transmitting the Bluetongue virus to an uninfected ruminant is dependent on environmental temperature (i.e. at higher average ambient temperatures this period is shorter).   

Official confirmation of the presence of Bluetongue in a country (or region) occurs when it is demonstrated by laboratory tests that the Bluetongue virus (BTV) is circulating between midge vectors and susceptible ruminant hosts in an area.

GB remained part of a Protection Zone for BTV8 since the first case of disease in 2007. In June 2010 GB changed its status to Lower Risk Zone for BTV8 which offered protection against the risk of disease from imported animals, and was an important step toward BTV freedom.
The last case of Bluetongue detected in Great Britain was in 2008 (detected as a result of post-import testing) and through our surveillance we have now been able to demonstrate to the European Commission that we have had no cases for the last two years and can officially be declared free of BTV8.

The current disease situation is that GB was officially declared to be free from Bluetongue on 5th July 2011.

The key implications for GB livestock keepers are:

  • There are no further Bluetongue specific restrictions on exporting sheep and cattle from Great Britain. For other export conditions please refer to the International trade pages of the Defra website;
  • Under EU law livestock keepers in GB will no longer be permitted to vaccinate against BTV8 or any other Bluetongue serotype
  • Current  import controls remain for susceptible livestock entering GB from BTV restricted zones across Europe (for further information please refer to the International trade pages of the Defra website)

Livestock keepers are strongly encouraged to remain vigilant and report any clinical signs of disease, including in animals that have previously been vaccinated against BTV8.

For further information:

HOW TO RECOGNISE THE DISEASE

What to look for

Bluetongue is characterised by changes to the mucous linings of the mouth and nose and the coronary band of the foot. Clinical signs can vary by species - although symptoms are generally more severe in sheep, cattle can also show signs of disease.

Clinical signs in sheep:

  • Eye and nasal discharges which become thick and crusty.
  • Drooling as a result of swelling and/or ulcerations in the mouth.
  • Higher than normal body temperature.
  • Swelling of the neck and/or the face, especially around the eyes and
    the muzzle.
  • Severe lameness - affected sheep are reluctant to rise.
  • Haemorrhages into or under the skin.
  • Inflammation and pain at the junction of the skin and the horn of the
    foot – the coronary band.
  • Respiratory problems – difficulty breathing.
  • A “blue tongue” is rarely a clinical sign of infection.
  • Sheep are apparantly sick, look tired and lethargic.
  • Production losses may be prolonged and include infertility (especially
    in males) and reduced lambing percentages.
  • Flock mortality may reach as high as 70 per cent and those that survive
    may lose condition and experience reduced wool and meat production.

Clinical signs in cattle

It is possible that cattle will show no signs of illness, however clinical signs have included:

  • Nasal discharge.
  • Swelling of the neck and head, especially around the eyes and muzzle.
  • Conjunctivitis (red and runny eyes).
  • Swelling inside and ulceration of the mouth.
  • Swollen and/or reddened teats and vulva.
  • Tiredness.
  • Lameness.
  • Saliva drooling out of the mouth.
  • Fever.
  • Potential for long-term production losses in recovered animals,
    e.g. reduced milk yield.
  • The disease cannot always be diagnosed on clinical grounds and laboratory testing is required for disease confirmation.

Photos of clinical signs are available on the Defra website.

REDUCING THE RISK OF DISEASE

Bluetongue virus is not normally naturally transmitted directly between animals (although cases of transmission from an infected dam to its unborn offspring – so-called ‘transplacental infection’ – have been recorded). By far the most important route of virus transmission between animals is via the bites of infected midges (Culicoides). However, the possibility of mechanical transmission of the virus between herds/flocks and within a herd/flock by unhygienic practices (e.g. use of contaminated surgical equipment or hypodermic needles) cannot be excluded.

Sourcing of livestock
It is important to consider the risks and check the health and vaccination status of animals when sourcing any animals, both from within the UK or abroad.

Midge mitigation measures
No one measure will prevent midges (Culicoides) biting animals. However, the use of a combination of these measures will help reduce the risk of animals becoming infected with BTV. Culicoides breeding sites can be potentially reduced by:

  • Moving dung heaps away from livestock or covering with a plastic, watertight cover
  • Scraping the perimeters of heaps/slurry pits to a depth of 6-10cm (this is where the majority of larvae reside).

Housing of animals in an enclosed space (where the means are available close doors and cover entrances with mesh) during periods of peak Culicoide activity may reduce biting rates. Farmers should be aware of the midge conditions on their premises, for example bringing hill sheep into low land where midges are more prevalent would increase the risk of midges biting.

No insecticides are authorised specifically to act against Culicoides. Deltamethrin-based compounds have performed best in tests, however, they only offer limited coverage of animals and provide 1-2 days protection at best (as do other generic repellents)

Insecticides and repellants do not entirely remove the risk of an animal contracting bluetongue and Defra recognise their use on farms does not provide a practical and cost-effective control measure against bluetongue in most cases.

Application of insecticides for short-term protection of animals transiting BTV zones, or where required for specific livestock movements (i.e. licensed moves) can be required.

  • Animals and their vehicle must be treated prior to travel
  • The product used should be based on a synthetic pyrethoid (eg Deltamethrin) and hold a GB marketing authorisation
  • Insecticide should be used in accordance with manufacturer’s instructions.

Spraying at rates beyond the manufacturer’s instructions will not improve efficacy and increases the risk of groundwater and surface water pollution. Synthetic pyrethoids are highly toxic to insect life in rivers and streams. Take great care not to allow these products to enter surface of groundwater. In particular, spraying vehicles on a hard stand presents particular dangers as run-off can be concentrated.

Treatment of the general environment with insecticides is not recommended, as this will have little effect on midge populations and has serious environmental implications.

REDUCING THE IMPACT OF DISEASE

Details of the UK’s Bluetongue control strategy are available from the Defra website. Thus strategy seeks to prevent disease spread through restriction of animal movement and vector control measures. Broadly, the controls can be summarised as follows:

  • Veterinary investigation on suspect premises, and restrictions which includes a ban on movement of susceptible animals on and off the premises
  • On confirmation that bluetongue virus is circulating, a Restricted Zone (RZ) will be declared around the infected premises. The RZ may consist of:

    - A Protection Zone (at least 100km radius around an IP)

    - Surveillance Zone (at least 50km in radius beyond the PZ).

As bluetongue is spread via vectors (i.e. midges), rather than from animal to animal, compulsory slaughter of ruminants infected with Bluetongue is not normally part of the control strategy. However, it may occasionally be considered e.g. to prevent introduction of disease into a BTV free area by recent importation of an infected animal (on a case by case basis depending on the epidemiological circfumstances), or indicated on animal welfare grounds in severly affected clinical cases.

Movement restrictions

Several other European member states remain subject to restrictions for Bluetongue of various serotypes. Imports of susceptible livestock from these restricted zones are subject to additional import controls.

Further information (including a map) on the Bluetongue restrictions applying to other European member states can be found on the European Commission website. Information on importing BTV susceptible animals can be found on the International Trade pages of the Defra website.

Legislation

Further information on Bluetongue disease, control measures and legislation applying in the relevant administartions are available from the following websites:

Page last modified: 22 July, 2011